1. Field of the Invention
This invention relates to an overcurrent protection circuit, and more particularly to a circuit for protecting the switching elements in an inverter (DC-AC power converter) against damage from an overcurrent by instantaneously breaking an input current and a driving signal of a switching regulator, when the input current of the inverter having the switching regulator exceeds a set point.
2. Prior Art
Heretofore, an inverter and a switching regulator driving the inverter are generally made up of semiconductor switching elements. Because electric resistance, when the elements are energized, is not zero, it is desirable to hold the applied voltage of the elements high in order to hold the efficiency of the inverter high. However, high-voltage switching elements are generally expensive, and it has to be equipped with means for preventing damages of the switching elements to maintain reliability of the apparatus. Up to now, an instantaneously breakable fuse and an instantaneous circuit breaker have been used. However, the fuse and breaker are slow to react upon overcurrent. More specifically, since the electro-static capacity of a capacitor connected to the switching regulator for supplying a current to the inverter is large, the switching elements in the inverter have been energized and damaged before the switching regulator was switched off. Also, because the overcurrent flows through the switching elements before the instantaneously breakable fuse and instantaneous circuit breaker functioned, there would occur degraded portions in the elements, with the result that the switching elements are rendered unable to function as properaly as they should.